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V. V. Flambaum

Publications and source records attributed to V. V. Flambaum.

At least 343 records · Page 19Linked to original sources
arXiv2005

Improved calculation of relativistic shift and isotope shift in Mg I

We present an ab initio method of calculation of isotope shift and relativistic shift in atoms with a few valence electrons. It is based on an energy calculation involving combination of the configuration interaction method and many-body perturbation theory. This work is motivated by analyses of quasar absorption spectra that suggest that the fine structure constant, alpha, was smaller at an early epoch. Relativistic shifts are needed to measure this variation of alpha, while isotope shifts are needed to resolve systematic effects in this study. The isotope shifts can also be used to measure isotopic abundances in gas clouds in the early universe, which are needed to study nuclear reactions in stars and supernovae and test models of chemical evolution. This paper shows that isotope shift in magnesium can be calculated to very high precision using our new method.

physics.atom-ph↗
arXiv2005

The radiative potential method for calculations of QED radiative corrections to energy levels and electromagnetic amplitudes in many-electron atoms

We derive an approximate expression for a "radiative potential" which can be used to calculate QED strong Coulomb field radiative corrections to energies and electric dipole (E1) transition amplitudes in many-electron atoms with an accuracy of a few percent. The expectation value of the radiative potential gives radiative corrections to the energies. Radiative corrections to E1 amplitudes can be expressed in terms of the radiative potential and its energy derivative (the low-energy theorem): the relative magnitude of the radiative potential contribution is ~alpha^3 Z^2 ln(1/(alpha^2 Z^2)), while the sum of other QED contributions is ~alpha^3 (Z_i+1)^2, where Z_i is the ion charge; that is, for neutral atoms (Z_i=0) the radiative potential contribution exceeds other contributions ~Z^2 times. The advantage of the radiative potential method is that it is very simple and can be easily incorporated into many-body theory approaches: relativistic Hartree-Fock, configuration interaction, many-body perturbation theory, etc. As an application we have calculated the radiative corrections to the energy levels and E1 amplitudes as well as their contributions (-0.33% and 0.42%, respectively) to the parity non-conserving (PNC) 6s-7s amplitude in neutral cesium (Z=55). Combining these results with the QED correction to the weak matrix elements (-0.41%) we obtain the total QED correction to the PNC 6s-7s amplitude, (-0.32 +/- 0.03)%. The cesium weak charge Q_W=-72.66(29)_{exp}(36)_{theor} agrees with the Standard Model value Q_W^{SM}=-73.19(13), the difference is 0.53(48).

physics.atom-ph↗
arXiv2005

Enhancement of nuclear Schiff moments and time reversal violation in atoms due to combination of soft nuclear octupole and quadrupole vibrations

Nuclear forces violating parity and time reversal invariance P,T-odd produce P,T-odd nuclear moments, for example, the nuclear Schiff moment. In turn, this moment can induce the electric dipole moment (EDM) in the atom. The contribution to the Schiff moment from the soft collective quadrupole and octupole vibrations in spherical nuclei is calculated in the framework of the quasiparticle random phase approximation with separable quadrupole and octupole forces. The values of nuclear Schiff moments predicted for odd 217-221Ra and 217-221Ra isotopes indicate a possibility of enhancement by a factor of 50 or more as compared to the experimentally studied spherical nuclei 199Hg and 129Xe. Since the EDM in very heavy atoms, such as Ra, Rn, and Fr, has an additional enhancement rapidly increasing with nuclear charge $Z$, the EDM enhancement can exceed two orders of magnitude. We discuss the nuclear structure effects causing an enhancement of the Schiff moment.

nucl-th↗
arXiv2005

Relativistic corrections to the nuclear Schiff moment

Parity and time invariance violating ($P,T$-odd) atomic electric dipole moments (EDM) are induced by interaction between atomic electrons and nuclear $P,T$-odd moments which are produced by $P,T$-odd nuclear forces. The nuclear EDM is screened by atomic electrons. The EDM of a non-relativistic atom with closed electron subshells is induced by the nuclear Schiff moment. For heavy relativistic atoms EDM is induced by the nuclear local dipole moments which differ by 10-50% from the Schiff moments calculated previously. We calculate the local dipole moments for ${^{199}{\rm Hg}}$ and ${^{205}{\rm Tl}}$ where the most accurate atomic and molecular EDM measurements have been performed.

nucl-th↗
arXiv2005

Causality condition and reflection on event horizon

A new way to implement the causality condition on the event horizon of black holes is discovered. The metric of a black hole is shown to be a function of the complex-valued gravitational radius r_g => r_g + i0. The relation between this modification of the metric and the causality condition is established using the analyticity of the S-matrix, which describes scattering of probing particles on a back hole. The found property of the metric has strong manifestations in scattering and related phenomena. One of them is the unexpected effect of reflection of incoming particles on the event horizon, which strongly reduces the absorption cross section.

gr-qc↗
arXiv2005

Relativistic energy shifts in Ge II, Sn II and Pb II and search for cosmological variation of the fine structure constant

Sensitivity of atomic transition frequencies to variation of the fine structure constant $α=e^2/\hbar c$ increases proportional to $Z^2$ where $Z$ is the nuclear charge. Recently several lines of heavy ions Ge II, Sn II and Pb II have been detected in quasar absorption spectra. We have performed accurate many-body calculations of $α^2$-dependence of transition frequencies ($q$-coefficients) for these atoms and found an order of magnitude increase in sensitivity in comparison with atomic transitions which were previously used to search for temporal and spatial variation of $α$ in quasar absorption systems. An interesting feature in Pb II is highly non-linear dependence on $α^2$ due to the level pseudo-crossings.

astro-ph↗
arXiv2004

Limits on a Dynamically Varying Fine Structure Constant

We show that using the modified form of the Dirac Hamiltonian as suggested by Bekenstein, does not affect the analysis in [1-4] of QSO data pertaining to a measurement of alpha variation. We obtain the present time limit on Bekenstein's parameter, tan^{2}chi =(0.2 \pm 0.7)\times10^{-6}, from the measurement of the hydrogen 2p fine structure using value of alpha obtained from different experiments.

astro-ph↗
arXiv2004

Tunneling into black hole, escape from black hole, reflection from horizon and pair creation

Within classical general relativity, a particle cannot reach the horizon of a black hole during a finite time, in the reference frame of an external observer; a particle inside cannot escape from a black hole; and the horizon does not produce any reflection. We argue that these processes may possibly be allowed in the quantum world. It is known that quantum mechanics allows pair creation at the horizon (one particle inside, another particle outside) and Hawking radiation. One can extend this idea to propose other processes. Tunneling of an external particle inside black hole may be produced by the creation of a pair at the horizon, followed by the annihilation of one created particle with the initial particle outside, with the other created particle appearing inside. Escape of a particle from a black hole may result from the creation of a pair, followed by the annihilation of one created particle with the particle inside, with the other created particle appearing outside. The escape may allow the transfer of information to the outside.Finally, the reflection of an external particle from the horizon may be modelled by a combination of the two processes presented above. The relationship between these "pair creation-annihilation'' mechanisms and the "horizon tunneling" calculations [1-5] is discussed.

gr-qc↗
arXiv2004

Atomic Clocks and the Search for Variation of the Fine Structure Constant

Evidence that the fine structure constant, alpha, was different in an early epoch has recently been found in quasar (QSO) absorption spectra. An accurate laboratory measurement of alpha variation could help to distinguish between space and time variation of alpha and possibly confirm the QSO results. We have performed calculations of the relativistic energy shifts that a variation of alpha would cause in a wide range of atomic spectra. A laboratory measurement of how these transition frequencies vary over time is vital in determining whether alpha is varying today.

physics.atom-ph↗
arXiv2004

Space-time variation of the fine structure constant and evolution of isotope abundances

At present several groups are analyzing astrophysical data in a search for time-variation of the fine structure constant $α$. Here we discuss how to exclude systematic effects caused by the changes in the isotope abundances during the evolution of the universe. We suggest using particular combinations of the transition frequencies of O II, Al II, Al III, Si II and Mn II as anchors, which are insensitive to $α$-variation and to changes in isotope abundances. These anchors can be used to determine the cosmological redshift. Then, one can use other combinations of frequencies as probes for the time-variation of $α$ and another set as probes for the isotopic abundances. In this way it is possible to eliminate one source of the systematic errors in the search for $α$-variation and get new information about evolution of the isotopes. On the level of accuracy that has already been reached in the search for $α$-variation it is possible to see ~10% changes in isotope abundances of Si and Ni.

astro-ph↗
arXiv2004

Reflection on event horizon and escape of particles from confinement inside black holes

Several recently found properties of the event horizon of black holes are discussed. One of them is the reflection of the incoming particles on the horizon. A particle approaching the black hole can bounce on the horizon back, into the outside world, which drastically reduces the absorption cross section in the infrared region. Another, though related phenomenon takes place for particles inside the horizon. A locked inside particle has, in fact, an opportunity to escape into the outside world. Thus, the confinement inside the horizon is not absolute. The escape from within the interior region of the horizon allows the transfer of information from this region into the outside world. This result may help resolve the information paradox for black holes. Both the reflection and escape phenomena happen due to pure quantum reasons, being impossible in the classical approximation.

gr-qc↗
arXiv2004

The alpha-dependence of transition frequencies for some ions of Ti, Mn, Na, C, and O, and the search for variation of the fine structure constant

We use the relativistic Hartree-Fock method, many-body perturbation theory and configuration-interaction method to calculate the dependence of atomic transition frequencies on the fine structure constant, alpha. The results of these calculations will be used in the search for variation of the fine structure constant in quasar absorption spectra.

physics.atom-ph↗
arXiv2004

Relativistic effects in two valence electron atoms and ions and the search for variation of the fine structure constant

We perform accurate calculations of the dependence of transition frequencies in two valence electron atoms and ions on a variation of the fine structure constant, alpha. The relativistic Hartree-Fock method is used with many-body perturbation theory and configuration interaction methods to calculate transition frequencies. The results are to be used in atomic-clock-type laboratory experiments designed to test whether alpha varies in time.

physics.atom-ph↗
arXiv2004

Limits on the temporal variation of the fine structure constant, quark masses and strong interaction from quasar absorption spectra and atomic clock experiments

We perform calculations of the dependence of nuclear magnetic moments on quark masses and obtain limits on the variation of $(m_q/Λ_{QCD})$ from recent measurements of hydrogen hyperfine (21 cm) and molecular rotational transitions in quasar absorption systems, atomic clock experiments with hyperfine transitions in H, Rb, Cs, Yb$^+$, Hg$^+$ and optical transition in Hg$^+$. Experiments with Cd$^+$, deuterium/hydrogen, molecular SF$_6$ and Zeeman transitions in $^3$He/Xe are also discussed.

hep-ph↗
arXiv2003

Configuration interaction calculation for the isotope shift in Mg I

We present an ab initio method of calculation of isotope shift in atoms with a few valence electrons, based on the configuration-interaction calculation of energy. The main motivation for developing the method comes from the need to analyze whether differences in isotope abundance in early universe can contribute to the observed anomalies in quasar absorption spectra. The current best explanation for these anomalies is the assumption that the fine structure constant, alpha, was smaller at early epoch. We show that we can calculate the isotope shift in magnesium with good accuracy.

physics.atom-ph↗
arXiv2003

Exponential enhancement of nuclear reactions in condensed matter environment

A mechanism that uses the environment to enhance the probability of the nuclear reaction when a beam of accelerated nuclei collides with a target nucleus implanted in condensed matter is suggested. The effect considered is exponentially large for low collision energies. For t + p collision the mechanism becomes effective when the energy of the projectile tritium is below $\sim$ 1 Kev per nucleon. The gain in probability of the nuclear reaction is due to a redistribution of energy and momentum of the projectile in several ``preliminary'' elastic collisions with the target nucleus and the environmental nuclei in such a way that the final inelastic projectile-target collision takes place at a larger relative velocity, which is accompanied by a decrease of the center of mass energy. The gain of the relative velocity exponentially increases the penetration through the Coulomb barrier.

nucl-th↗